/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.myfaces.jtracc.util;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;

/**
 * Various helpers to deal with exception
 * 
 * @author imario@apache.org
 */
public final class ExceptionUtils
{
	private ExceptionUtils()
	{
	}

	/**
	 * <p>
	 * returns a list of all throwables (including the one you passed in) wrapped by the given throwable.
	 * In contrast to a simple call to <code>getClause()</code> on each throwable it will also check if the throwable class
	 * contain a method <code>getRootCause()</code> (e.g. ServletException or JspException) and call it instead.
	 * </p>
	 * <p>
	 * The first list element will your passed in exception, the last list element is the cause. 
	 * </p>
	 */
	public static List getExceptions(Throwable cause)
	{
		List exceptions = new ArrayList(10);
		exceptions.add(cause);
		
		do
		{
			Throwable nextCause;
			try
			{
				Method rootCause = cause.getClass().getMethod("getRootCause", new Class[]{});
				nextCause = (Throwable) rootCause.invoke(cause, new Object[]{});
			}
			catch(Exception e)
			{
				nextCause = cause.getCause();
			}
			if (cause == nextCause)
			{
				break;
			}
			
			if (nextCause != null)
			{
				exceptions.add(nextCause);
			}
			
			cause = nextCause;
		}
		while (cause != null);
		
		return exceptions;
	}

	/**
	 * Find a throwable message starting with the last element.<br />
	 * Returns the first throwable message where <code>throwable.getMessage() != null</code> 
	 */
	public static String getExceptionMessage(List throwables)
	{
		if (throwables == null)
		{
			return null;
		}

		for (int i = throwables.size()-1; i>0; i--)
		{
			Throwable t = (Throwable) throwables.get(i);
			if (t.getMessage() != null)
			{
				return t.getMessage();
			}
		}
		
		return null;
	}
}
